In the specification of German published patent application DE 3 931 429A, this cavity, which is mainly defined by the primary coaxial part, is closed by centering means which are also arranged to act between the primary and secondary coaxial parts. As a result, since the torque limiter is also arranged within the Same cavity, the torque limiter is also lubricated by the grease, and this is detrimental to its torque limiting action. Another consequence of this arrangement is that, since the torque limiter gives rise to wear products, these wear products will inevitably contaminate the grease in the cavity, thus impairing its lubricating qualities.
In the specification of German published patent application DE 3 624 496A, the cavity in which the circumferentially acting resilient means are fitted is at least partly defined by a sealing means which includes either one or two thin rings, which, being suitably profiled, closely surround the circumferentially acting resilient means. These sealing rings make it necessary to provide special securing means, which in practice consist of welds, for attaching them to either one of the two coaxial parts. The assembly together of the various components of this arrangement is consequently somewhat complex, and this increases manufacturing costs.